Luminex screening for donor-specific anti-HLA antibodies in pancreas transplant alone

M. De Donno¹, D. Focosi¹, M. Occhipinti², P. Marchetti², F. Vistoli³, R. Duquesnoy⁴, U. Boggi³, F. Scatena^1
1 Division of Immunohematology - Pisa University Hospital, Pisa, Italy; ² Section of Transplant Endocrinology and Metabolism - Pisa University Hospital, Pisa, Italy; ³ Division of General and Transplant Surgery - Pisa University Hospital , Pisa, Italy; ⁴ Division of Cardiothoracic Anesthesia and Intensive Care - Pisa University Hospital, Pittsburgh, USA

Objective: The value of donor-specific anti-HLA antibodies (DSHA) at predicting graft failure has been established for many types of solid organ transplantations, but their role in pancreas transplant alone (PTA) has never been reported.

Methods: 83 PTAs were performed at the Pisa transplant centre from 2000 to 2010. Post-transplantation sera (median follow-up: 45 months; range 7-106) were available for 44 patients. Pre-and post-transplant recipient sera were screened for DSHA by Luminex. Using the HLA MatchMaker algorithm (www.hlamatchmaker.net), we calculated the number of mismatched eplets for A+B loci for each transplant in order to assess whether a higher load of mismatched eplets for agiven HLA locus could favor the onset of DSHAs.

Results: Among the 83 PTAs,the mean number of mismatched eplets was 15 (range 2-33). Among the 44 recipients with paired pre- and post-transplant sera, 14 recipients tested positive at baseline. At follow-up 13 of these 14 recipients remained sensitized, 1 seroreverted, and 6 more recipients seroconverted against class I antigens. There was no statistically significant difference in the mean numberof mismatched eplets on A+B loci in these latter 6 recipients vs. recipientsnot developing de novo anti-HLAantibodies (median 16 vs.15). After censoring for graft thrombosis and death with a functioning graft, only 5 of the 44 recipients had acute or chronic rejection and finally lose their grafts. Of them, 2 patients had pretransplant DSHA (MFIs: anti-A66 3,900; anti-A32 5,500, respectively) and rejected their PTA after 6 and 95 months, respectively. 3 more patients without pre-transplant DSHA seroconverted (MFIs:anti-B51 10,679 + anti-A24 7,960 + anti-DR1 1,123; anti-A2 1,708 + anti-DQ07 3,417;anti-DQ06 2,801) and all of them rejected within next year. Non-DSHAs had no predictive value for rejection.

Conclusions : Luminex testing can predict PTA rejection.